An antenna transmits/receives an electromagnetic wave by outputting a beam. It is needed that direction of the beam, i.e. tilting angle is adjusted in various directions. Accordingly, the antenna employs a phase shifter of dividing a power and a tilting adjustment apparatus, etc. so as to adjust the tilting angle.
Hereinafter, structure of common antenna will be described with reference to accompanying drawing.
FIG. 1 is a view illustrating schematically a conventional antenna.
In FIG. 1, the antenna includes a reflection plate 100, a phase shifter 102, a tilting adjustment apparatus 104 and a shaft 106.
The phase shifter 102 is connected electrically to radiators, divides the power into the radiators, and is formed on the reflection plate 100.
The phase shifter 102 includes a rotation member 108, a dielectric substrate 110, a line 112, a central axis member 114 and an arm member 116.
The tilting adjustment apparatus 104 is connected to the rotation member 108 of the phase shifter 102 through the shaft 106, and provides rotatory power to the rotation member 108 through the shaft 106 to rotate the rotation member 108 during adjustment of the tilting angle. Since the rotation member 108 is connected to the arm member 116 through the central axis member 114, the arm member 116 rotates in response to rotation of the rotation member 108. As a result, amount of the power fed to the radiators connected to both ends of the line 112 changes, and so the direction of the beam outputted from the radiators is changed.
The rotation member 108 is disposed on a rear surface of the reflection plate 100 as shown in FIG. 1, but the arm member 116, etc. is disposed on an upper surface of the reflection plate 100. Accordingly, the central axis member 114 should be formed through the reflection plate 100 so as to connect the arm member 116 to the rotation member 108. As a result, characteristics of the antenna such as isolation, PIMD, etc. may be deteriorated.
In addition, many components should be used on the rear surface of the reflection plate 100 to fix the rotation member 108 to the reflection plate 100.
In case that a user means to use the antenna as another usage, e.g. in another frequency band, shifting rate of the arm member 116 (distance of the arm member 116 shifted while the tilting adjustment apparatus 104 rotates by one time) need to be changed from initial setting. However, since one antenna may not change the shifting rate, the tilting adjustment apparatus 104 or the phase shifter 102 should be exchanged or the antenna should be replaced with another antenna. As a result, utilization of the antenna is lowered and exchanging cost increases.